Effect of fermented grape pomace on growth performance and intestinal health of weaned piglets.

The improvement of forage quality through proper fermentation is well documented. Grape pomace (GP), an economically valuable by-product, remains underutilized despite its potential benefits. This study explores the effects of fermented GP (FGP) supplementation on weaned piglets, focusing on immune and antioxidant capacity, intestinal flora homeostasis, growth performance, and diarrhea reduction. We first analyzed and compared the nutritional composition of GP before and after fermentation. Subsequently, a diet supplemented with 5% FGP was formulated. From an initial pool of 480 weaned piglets, 120 healthy animals (28 days old, average weight 8.42 ± 0.19 kg) were randomly assigned to two groups: a control group (CON) fed a basal diet and an experimental group receiving the 5% FGP-supplemented diet. The results demonstrated that fermentation significantly enhanced the levels of key nutrients and amino acids (e.g., Ca, P, Glu) in GP (P < 0.05). Dietary supplementation with FGP significantly improved feed efficiency, as indicated by a reduced feed-to-gain ratio (F/G), and decreased the incidence of diarrhea (P < 0.05). Additionally, FGP exhibited notable antioxidant activity, reflected by reduced serum malondialdehyde (MDA) levels and mitigation of oxidative stress (P < 0.05). Immunomodulatory benefits were also observed, including elevated serum immunoglobulin G (IgG) and interleukin-10 (IL-10), along with decreased tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) levels (P < 0.05). Morphological improvements in intestinal architecture were evident, with increased villus height (VH) in the duodenum, jejunum, and ileum, as well as an enhanced villus height-to-crypt depth ratio (V/C) (P < 0.05). In conclusion, dietary inclusion of FGP enhances disease resistance in piglets by improving antioxidant capacity, modulating immune responses, enhancing intestinal morphology, and enriching microbial diversity. These findings support FGP as a viable nutritional strategy for boosting health and optimizing the utilization of grape processing by-products.